Heller, 52, was a three-term congressman from the northern part of the state when he was appointed by Republican Gov. Brian Sandoval in May 2011 to fill out the term of GOP Sen. John Ensign, who resigned because of a sex scandal.

Berkley, 61, has made this race one of the tightest in the country — even while facing a House ethics probe.

Berkley is being investigated for her efforts to save southern Nevada's only kidney transplant program — just the sort of thing a member of Congress would do for her district. But it turns out that Berkley's husband is a kidney specialist whose business profits from the program.

"I did absolutely nothing other than what is important to the people that I represent, making sure that they get the best possible health care in this country and in this state," Berkley said this week, during the third and final debate with Heller.

Heller worked with Berkley to save the kidney transplant program, but said he didn't know at the time that Berkley's husband was a kidney doctor.

"I think the Heller campaign thought they'd put her away by now," says University of Nevada, Las Vegas political science professor David Damore. "The fact that she's been able to survive this and still be within the margin of error in most of the polling I think tells you that either voters have a really low level of expectation for their politicians, or that she's done a pretty good job of spinning the story."

Berkley also has the numbers on her side. Democrats now have about an 8-point registration advantage over Republicans in the state, which is why Heller has been pitching hard to independents, who make up nearly 18 percent of Nevada voters.

"There used to be a time when a good idea was a good idea, and it didn't matter whose idea it was," Heller said in an ad. "I support Democrat and Republican ideas when they're good for Nevada, and I oppose them when they're not."

Heller has even put some daylight between himself and the man at the top of the Republican ticket, says Damore.

"For example, after [Mitt Romney's] '47 percent' dust-up a few weeks ago, [Heller] was very quick to point out how members of his family had used government services and he didn't take that point of view," says Damore. "When Romney came in for a rally in southern Nevada, Heller was nowhere to be found."

But that hasn't stopped Berkley from trying to paint Heller as a knee-jerk GOP loyalist.

Nevadans can hear these attacks and more 24 hours a day, seven days a week. All they have to do is turn on the TV. Las Vegas is one of the most saturated media markets in the country when it comes to political advertising.

The Senate campaigns are just a part of that. There is also the presidential campaign and a couple of hard-fought congressional races. And then there are the outside groups: Karl Rove's Crossroads GPS, for example, has spent $3 million attacking Berkley in just the past couple of months.

And Crossroads GPS just announced it's going to spend another million dollars against Berkley in the coming week.

But with the piles of money being spent on TV advertising here, most polls continue to show the Senate race is a dead heat. And the only Nevadans who aren't tired of this show probably own TV stations.

Copyright 2013 NPR. To see more, visit http://www.npr.org/.

Transcript

ROBERT SIEGEL, HOST:

From the presidential contest, now to one of the tightest Senate races in the country. It's in Nevada where early voting begins this Saturday. The GOP's hopes of capturing a majority in the Senate depends in part on their Nevada candidate, Dean Heller. He is the incumbent in the race. The former three-term congressman was appointed to finish the term of Republican Senator John Ensign, who resigned because of a sex scandal.

NPR's Ina Jaffe reports that Heller's Democratic opponent has made this a remarkably close race, even though she is the subject of an ethics probe.

INA JAFFE, BYLINE: Seven-term Congresswoman Shelley Berkley is being investigated for her efforts to save southern Nevada's only kidney transplant program, just the sort of thing a member of Congress would do for her district. But it turns out that Berkley's husband is a kidney specialist whose business profits from the program.

JAFFE: Veteran political reporter Jon Ralston was the moderator of the final debate between Berkley and Heller this week. And the congresswoman said she had no doubt she'd ultimately be exonerated.

REPRESENTATIVE SHELLEY BERKLEY: I did absolutely nothing other than what is important to the people that I represent, making sure that they get the best possible health care in this country and in this state.

JAFFE: Dean Heller worked with Berkley to save the kidney transplant program, but he told moderator Jon Ralston he didn't know at the time that Berkley's husband was a kidney doctor.

SENATOR DEAN HELLER: And she never brought it to my attention, either.

BERKLEY: Wait a minute.

HELLER: And I wish she had, actually.

BERKLEY: Why? Would you have voted against it?

HELLER: We probably would have had a different discussion.

JON RALSTON: What would the discussion have been?

HELLER: That perhaps you ought to be a little bit more careful if she, in fact, did have a conflict.

DAVID DAMORE: I think the Heller campaign thought they would've put her away by now.

JAFFE: David Damore teaches political science at the University of Nevada, Las Vegas.

DAMORE: The fact that she's been able to sort of survive this and still be within the margin of error in most of the polling I think tells you that either voters have a really low level of expectation for their politicians or that she's done a pretty good job of spinning the story.

JAFFE: Berkley also has the numbers on her side. Democrats now have about an 8-point registration advantage over Republicans, which is why Heller has been pitching hard to independents, who make up nearly 18 percent of Nevada voters.

HELLER: Used to be a time when a good idea was a good idea, and it didn't matter whose idea it was. I support Democrat and Republican ideas when they're good for Nevada.

JAFFE: Heller has even put some daylight between himself and the man at the top of the GOP ticket, says David Damore.

DAMORE: For example, after the 47 percent dust-up a few weeks ago, he was very quick to point out how members of his family had used government services and he didn't take that point of view. When Romney came in for a rally in southern Nevada, Heller was nowhere to be found.

JAFFE: But that hasn't stopped Shelley Berkley from trying to paint Heller as a knee-jerk GOP loyalist.

JAFFE: Nevadans can hear these attacks and more 24 hours a day, seven days a week. All they have to do is turn on the TV. Las Vegas is one of the most saturated media markets in the country when it comes to political advertising. The Senate campaigns are just a part of that. There are also the presidential campaigns and a couple of hard-fought congressional races.

And then there are the outside groups. For example, Karl Rove's Crossroads GPS has spent $3 million attacking Berkley in just the last couple of months.

JAFFE: And Crossroads just announced they're going to spend another million dollars against Berkley in the coming week. But with the piles of money being spent on TV advertising here, most polls continue to show the Senate race is a dead heat. And the only Nevadans who aren't tired of this show probably own TV stations.